Explanation : Indifference curves for normal goods have not only a negative slope, but are also convex with reference to the origin. The convexity of the indifference curves implies that: ∎ The two goods are imperfect substitutes for one another. ∎ The MRS between the two goods decreases as a consumer moves along an indifference curve. Convexity in the indifference curve is caused by the diminishing MRS. Properties of Indifference Curve Indifference curves have the following four basic properties: 1. Indifference curves have a negative slope; 2. Indifference curves of imperfect substitutes are convex to the origin; 3. Indifference curves do not intersect nor are they tangent to one another; 4. Upper indifference curves indicate a higher level of satisfaction.